Green’s Dictionary of Slang

1. a scar.

1958

F. Norman Bang To Rights 69: Where did yer get yer tram line?

2. a thin shaved line in an eyebrow, or a thin line of short hair on a shaved head; usu. in pl.

2000		Guardian Guide 22–28 May 12: Five years after they were fashionable, I recently decided to get tramlines.
2004		Argos.co.uk 🌐 Slim blade for intricate designs such as tramlines, goatees and hair art.